Electron beam welder incorporating sliding seal means

ABSTRACT

The present invention relates to apparatus for welding by means of an electron beam and describes a sealing system which allows a machine member carrying an electron beam gun and a second member carrying parts to be welded to slide one with respect to the other while maintaining a low pressure in the electron gun and the area surrounding the parts to be welded. The sliding seal apparatus is applied to linear or rotary translation of the electron beam gun support means with respect to the work holding means.

United States Patent [1 1 [11] 3,742,365 Sciaky 5] June 26, 1973'ELECTRON BEAM WELDER 3,626,142 12/1971 King 219 121 EB INCORPORATINGSLIDING SEAL MEANS David Sciaky, Chicago, 111.

Assignee: Welding Research, Inc., Chicago, 111.

Filed: Feb. 15, 1972 Appl. No.: 226,611

lnventor:

US. Cl. 219/121 EB, 285/DIG. 19 Int. Cl B23k 15/00 Field of Search219/121 R, 121 BB, 219/121 EM; 277/94, 214, 215; 285/DIG. 18, DIG. 19

References Cited UNITED STATES PATENTS 12/1965 Windebank 219/121 EBPrimary Examiner-J. V. Truhe Assistant Examiner-Gale R. PetersonAttorney-Julius L. Solomon [57] ABSTRACT The present invention relatesto apparatus for welding by means of an electron beam and describes asealing system which allows a machine member carrying an electron beamgun and a second member carrying parts to be welded to slide one withrespect to the other while maintaining a low pressure in the electrongun and the area surrounding the parts to be welded. The sliding sealapparatus is applied to linear or rotary translation of the electronbeam gun support means with respect to the work holding means.

7 Claims, 6 Drawing Figures PATENTEDJUNZS m5 SIIEIIUIB lll FIG. 2

FIG. 3

ELECTRON BEAM WELDER INCORPORATING SLIDING SEAL MEANS The presentinvention relates to apparatus for welding by means of an electron beamand, more specifically, to a sealing method and system which allows amachine member carrying an electron beam gun to slide with respect to avacuum chamber which is provided with a means whereby the electron beamgenerated in the electron gun may pass from the externally mountedelectron gun into the evacuated chamber in which parts to be welded aremounted.

In the past, attempts have been made to utilize machines of this naturebut experience has shown that the sealing means between the plates whichslide one with respect to the other have proven to be unsatisfactory,being subject to rapid wear, excessive frictional resistance between thetwomoving parts and leakage of gas, rendering the seal ineffective. Anexample of this old type of sealing means is illustrated in U.S. Pat.No. 3,136,883. When using an O-ring seal, as is described in this latterpatent, it is found that the motion of the sliding plate runningparallel to the O-ring seal causes the seal to bunch up and wrinkle asit is urged in the direction of travel of the plate so that soon a leakdevelops at the leading end of the seal. The bunching up of the O-ringcreates a resistance to motion of the plateand, due to the pressureconcentrated at the high point of the O-ring, the O-ring wears unevenly.

- It is the purpose of the present invention to provide a sealing meanswhich will overcome these defects and inconveniences. An object of thepresent invention is to provide a sealing means utilizing ordinaryO-rings which have an exceptionally long life. Another object is toprovide an O-ring sliding seal system in which the frictional resistancedoes not change during the stroke over the length of the sliding motion;Another object is to provide a sliding seal that is effective forsealing parts in either linear or circular motion with respect to oneanother.

The invention may better be understood by referring to the accompanyingdrawings.

FIG. 1 is a perspective view of an electron beam welding machine whichincorporates a sliding seal in accordance with the present invention.

FIG. 2 is a top view of a seal plate carrying an O-ring seal inaccordance with the prior art, and,

FIG. 3 is a top view of a linear motion seal plate made in accordancewith the present invention.

FIG. 4 illustrates an electron beam welding machine incorporating thenovel sliding seal means which utilizes a dial feed work transportmechanism for use in high production applications.

FIGS. 4A and 4B illustrate some details of the dial feed machine of FIG.4.

FIG. 1 illustrates a typical electron beam welding machine utilizing thesliding seal of the present invention. The rigid framework 1 supportsthe electron beam chambers 2 and 3 which adjoin each other. The slidingseal plate 8 covers the two vacuum chambers and carries in a groovewhich has been milled: into its upper surface a conventional O-ringcontinuous flexible seal. The electron beam gun mounted in the gunhousing 6 is supported on the structure 7 which is designed: to slide,in the direction indicated by the arrows, on the seal plate 8. The sealplate 8 has a slot machined along a portion of its length through whichthe electron beam generated by the electron gun is allowed to pass intothe vacuum chambers so as to impinge upon the work pieces to be welded.A motorized ball screw drive 11 is provided to actuate the gun support 7carrying the electron beam gun so that it may be caused to move from oneend of its travel to the other. Vacuum pumps 9 and 10 are provided toevacuate the welding chambers 2 and 3. Work clamping means are providedwithin the chamber and work drive means 4 and 5 are provided to move thework within the chamber during the welding operation so that welding maybe accomplished along a desired path. A high voltage power supply 12provides the power supplies required to generate and accelerate theelectron beam and a control cabinet 13 contains all the control requiredto operate the machine. In operating the machine, chambers 2 and 3 areat first open to allow the work pieces to be mounted on the toolingwithin the chambers. The chambers are then closed and evacuated to thepressure required for welding approximately microns the electron beamgun adjusted in position over one of the piece parts, and the welding ofthe first piece start then accomplished. The gun support and housing isthen slid over the seal plate so that the electron gun is in the properposition for the welding of the part in the second chamber. While thewelding is going on in the second chamber, the first chamber is openedto the atmosphere, the welded part removed and another unwelded partplaced in the tooling. The chamber is then pumped down and when thewelding is completed in the second chamber, the gun support is slid overthe seal plate 8 so that the electron beam gun is in the proper positionover the piece part in the first chamber.

Another type of machine may require the welding of a continuous seamperhaps 30 to 40 inches long. In this case only one vacuum chamber wouldbe required into which the parts would be placed and the gun supportslide 7 would move along the sliding sealplate 8 for the length of the30 or 40 inch travel required.

FIG. 2 illustrates the configuration of the seal which has been usedpreviously for this type of work. The O- ring 14 is mounted in a groovewhich for most of its length runs parallel to the motion. When the gunsupport slide moves in the direction as indicated by the arrow over thestationary seal plate 15, the material in the O-ring 14 is forcedtowards the right. The seal material bunches up, wrinkles form, creatingopenings so that the air may leak into the vacuum chamber and increasethe pressure so that the electron beam welding process cannot continue.

FIG. 3 illustrates the sliding seal plate made in accordance with thepresent invention. An ordinary O-ring seal is placed in the groove whichhas been milled along a path as shown by the dotted lines in FIG. 3.When the support plate 7 carrying the electron beam gun moves in thedirection of the arrow there will be no bunching or wrinkling of theO-ring inasmuch as the motion of the support plate 7 is alwaystransverse to the O-ring. The O-ring being backed up by thesides of theO-ring groove cannot bunch in this direction but merely rolls slightlyto the side wall of the groove and is supported by it. It has beenfound'that seal plates utilizing the zigzag O-ring groove path as shownin FIG. 3 operate smoothly and retain their sealing ability and haveexceedingly long life and make it possible to produce electron beamwelding machines which will operate reliably and satisfactorily withoutexceptional maintenance over long periods of time so that the electronbeam welding process for high production industry becomes practical.

FIG. 4 illustrates an electron beam welding machine for use in highproduction industry to produce parts at high speeds on a continuousbasis. The machine includes a circular table 16 which incorporates anumber of scalable pockets 17 disposed at equal distances from eachother along a circle towards the edge of the plate and a seal plateagainst which the table slides so as to bring a different group ofpockets to predetermined positions under the seal plate intermittently.Parts to be electron beam welded may be placed upon a suitable fixturewithin the pocket 17 at the position A on the table 16 and the tablecaused to rotate by an automatic indexing mechanism 18 which indexes thetable intermittently from the loading position into a first prepumpingstation and then through a second pumping area where the pocket ispumped down to the pressure suitable for welding, to a positionunderneath the electron beam gun 19 at which point the part is weldedduring the dwell time of the indexing mechanism. The part continues thenthrough a pre-ejection area and finally to the ejection station E whereit may be unloaded from the machine.

O-ring seals are arranged on the seal plate 22 in the configurationshown by the dotted lines on FIG. 48 so as to form two separate volumesbetween the table 16 and the seal plate 22. An inner volume enclosed bythe inner seal 23 and a second volume between the inner seal 23 and theouter seal 24. The inner O-ring seal of zig-zag configuration closes offthe area around the pocket containing the part underneath the weldinggun. The second outer seal 24 of zig-zag configuration seals off thevolume surrounding the first seal 23. The sealing plate 22 is connectedto a first pumping means, through a hole 25 in the seal plate and piping21, which partially evacuates the pocket 17 which is in the firstpumping station. A second pumping means through the tubing 20 and asecond hole 26 in the seal plate evacuates the space enclosed by theinner seal 23. The electron beam gun is disposed over a third hole 27 inthe seal plate through which the electron beam may pass and is supportedand sealed in such a way that the pocket carrying the piece part whichis directly below the gun may easily be maintained at a pressure ofapproximately 50 to 100 microns.

FIG. 4A is a section taken at the welding station of a portion of therotating table 16 showing one of the scalable pockets 17 and tooling 28used to hold the parts 29 and 30 being welded. In the case illustratedthe weld is made along the circular path 32 which defines the jointbetween the parts 29 and 30. The electron beam 31 is caused to traversethe circular path 32 through the action of suitable and well knownelectron beam deflection means associated with the electron gun. Theelectron gun housing 33 is fitted to the seal plate 22 through the hole27 and is sealed to the seal plate with flexible seals 34 so that thespace below the gun may be maintained at the desire d gas pressure.

By means of this seal plate the small inner volume containing the pocketholding the part which is to be welded is sealed and pumped and thesecond volume surrounding the first volume between the seal plate andthe rotating disk is maintained at some slightly higher transitionalpressure between the atmospheric pressure and the pressure required atthe welding position. By

means of the novel zig-zag configuration of the flexible sealing meansutilized to form the seal between the seal plate and the rotating turntable it has been found that the turn table may be operated on acontinuous basis for exceedingly long periods of time without excessivewear of the sealing means. Bunching and wrinkling of the O-ring iseliminated and dial feed machines for the electron beam welding of partsat high production rates become feasible, practical and economical.

Although specific forms have been illustrated to describe the invention,the invention is not limited to these forms or to such modification ofthem as may be obvious to the skilled man of the art.

What I claim is:

1. An electron beam welding machine for the continuous welding of partsin series comprising a circular table, a seal plate disposed above saidcircular table, sealable pockets arranged equidistant from each otheradjacent the outer edge of the said table, means within said pockets forsupporting workpieces to be welded by an electron beam means forrotating the said table in stepwise fashion against a pair of continuousflexible seals mounted in zig-zag concentric form upon the said sealplate so as to form two sealed spaced between the table and the sealplate, means for positioning one of said pockets so that it communicateswith one of said spaces which is maintained at a desired weldingpressure while the following pocket ispositioned so that it communicateswith the second space which is main tained at a pressure intermediate tothe atmospheric pressure and the welding pressure so as to partiallyevacuate the pocket, means for evacuating each of said spaces, means forgenerating, focusing and deflecting a beam of electrons, and means forindexing each of said pockets in sequence into a position under the saidelectron beam means for a preset interval of time.

2. An electron beam welding machine, as in claim 1, wherein said pair offlexible seals comprises, at least two endless resilient flexiblesealing means supported on a single plane of the said fixed member andarranged so that each one is positioned wholly within the one nextlargest so as to form separate sealed spaces bounded by the innermostseal and the said fixed and movable members and between each pair ofadjacent seals and the said fixed and movable members, the said sealingmeans being so arranged that it does not lie tangent to a line parallelto the direction of motion of the movable member except at such pointswhere there is a reversal in path of the seal transverse to thedirection of motion.

3. An electron beam as in claim 2 welding machine which each of the saidspaced communicates with a separate vacuum pump.

4. An electron beam welding machine as in claim 2 in which each of saidspaces is maintained at a progressively lower gas pressure with thehighest pressure in the outermost space.

5. An electron beam welding machine as in claim 2 in which each of thesaid flexible seals is arranged in zig-zag form.

6. An electron beam welding machine as in claim 2 comprising two of saidendless seals.

7. An electron beam welding machine as in claim 6 in which the pressurein the innermost space is maintained at a gas pressure of approximately50 microns and the pressure in the second space between the two saidseals is maintained at a pressure intermediate to 50 microns and theatmospheric pressure.

it I. t t

1. An electron beam welding machine for the continuous welding of partsin series comprising a circular table, a seal plate disposed above saidcircular table, sealable pockets arranged equidistant from each otheradjacent the outer edge of the said table, means within said pockets forsupporting workpieces to be welded by an electron beam means forrotating the said table in stepwise fashion against a pair of continuousflexible seals mounted in zig-zag concentric form upon the said sealplate so as to form two sealed spaced between the table and the sealplate, means for positioning one of said pockets so that it communicateswith one of said spaces which is maintained at a desired weldingpressure while the following pocket is positioned so that itcommunicates with the second space which is maintained at a pressureintermediate to the atmospheric pressure and the welding pressure so asto partially evacuate the pocket, means for evacuating each of saidspaces, means for generating, focusing and deflecting a beam ofelectrons, and means for indexing each of said pockets in sequence intoa position under the said electron beam means for a preset interval oftime.
 2. An electron beam welding machine, as in claim 1, wherein saidpair of flexible seals comprises, at least two endless resilientflexible sealing means supported on a single plane of the said fixedmember and arranged so that each one is positioned wholly within the onenext largest so as to form separate sealed spaces bounded by theinnermost seal and the said fixed and movable members and between eachpair of adjacent seals and the said fixed and movable members, the saidsealing means being so arranged that it does not lie tangent to a lineparallel to the direction of motion of the movable member except at suchpoints where there is a reversal in path of the seal transverse to thedirection of motion.
 3. An electron beam as in claim 2 welding machinewhich each of the said spaced communicates with a separate vacuum pump.4. An electron beam welding machine as in claim 2 in which each of saidspaces is maintained at a progressively lower gas pressure with thehighest pressure in the outermost space.
 5. An electron beam weldingmachine as in claim 2 in which each of the said flexible seals isarranged in zig-zag form.
 6. An electron beam welding machine as inclaim 2 comprising two of said endless seals.
 7. An electron beamwelding machine as in claim 6 in which the pressure in the innermostspace is maintained at a gas pressure of approximately 50 microns andthe pressure in the second space between the two said seals ismaintained at a pressure intermediate to 50 microns and the atmosphericpressure.